The High Court agreed. Mr Justice Tugendhat said in its ordinary meaning, the tweet meant Lord McAlpine, 71, was a paedophile who was guilty of sexually abusing boys in care.

If he was wrong, he would find it had an innuendo meaning to the same effect.

There will now be another hearing to decide damages unless the two sides can agree.

To say I’m surprised and disappointed by this is an understatement

Sally Bercow, speaker's wife

Mrs Bercow promptly tweeted her apologies and wrote letters apologising for the distress caused. But it was not enough to avoid a High Court showdown. She was “disappointed” by the ruling but Lord McAlpine’s lawyer said she had caused “unnecessary pain”.

In a statement, she said: “To say I’m surprised and disappointed by this is an understatement. However, I will accept the ruling.”

Damages are expected to be £50,000 with costs as high as £100,000 – meaning a £150,000 bill.

The BBC did not name Lord McAlpine but settled its defamation claim for £185,000.